It is well-known that a provider/operator of a communications network strives to increase the level of "survivability" of the network whenever a fault occurs, e.g., when a cable carrying communications is inadvertently cut. The operator typically increases the level of survivability by employing a protection-switching architecture to recover from a fault. Protection switching, as it is commonly referred to, involves establishing preassigned backup resources which are switched into service when a network failure occurs. Also, the effectiveness of a protection switching architecture is dictated by spare capacity constraints in the associated network, in which a so-called protected domain is usually independent of the bounds of an end-to-end service connection. Moreover, most protection-switching architectures use an end-to-end Signal Fail (SF) signal to cause the protection switching to switch to spare resources.
However, a problem arises when an end-to-end connection traverses different networks each providing its own protection switching. In that instance the boundaries of the protected domains respectively associated with the different networks are not clearly defined making it difficult for a switch in such a connection to determine quickly whether it should invoke protection switching when a failure occurs, which may result in a loss of information that is being transported over that connection.